Source: www.reddit.com

We bought a lot of fancy equipment and put it in a rack. Rack got too hot so we ran out to the local store and bought a regular $20 household fan and put it in the top of the rack as a temporary workaround. We then went and bought a special rack mounted fan for cooling racks for $350 and installed it and removed cheap fan. Rack overheated again. Went back to $20 fan.